Metal complex having β-diketonate, process for production thereof, photoelectric conversion element, and photochemical cell

ABSTRACT

A metal complex having a β-diketonate represented by the following formula (1):                    
     wherein M represents a metal atom of the VIII group, R 1 , R 2  and R 3  represent a group or an atom selected from the group consisting of an alkyl group, an aryl group, a hydroxyl group, an amino group, an alkoxy group, a hydrogen atom and a halogen atom; X −1  represents an ion selected from a halogen, nitric acid, sulfonic acid, fluoroboric acid, fluorophosphoric acid, or perchloric acid ion; L 1  or L 2  represents a 2,2′-bipyridine or 1,10-phenanthroline group where these groups may be substituted with a group or an atom selected from an alkyl group, a carboxyl group, a sulfonic acid group, a phosphonic acid group, a hydroxyl group, an amino group, a hydrogen atom and a halogen atom. A photoelectric conversion element and a photochemical cell using the above-mentioned metal complex.

This application is the national phase under 35 U.S.C. §371 of PCTInternational Application No. PCT/JP00/09254 which has an Internationalfiling date of Dec. 26, 2000, which designated the United States ofAmerica.

TECHNICAL FIELD

The present invention relates to a metal complex having a β-diketonate,a process for producing the same, a photoelectric conversion element,and a photochemical cell.

BACKGROUND ART

Inorganic semiconductors, such as a monocrystal, polycrystal, andamorphous silicon, are used as photoelectric conversion materials usedfor solar cells. These materials are pointed out to have the problemsthat they require large energy in a production process and containcomponents that are not environmentally preferable. To deal with theseproblems, an energy converter utilizing a photoelectric chemicalreaction that takes place at the boundary between a photo-semiconductorand an electrolytic solution, has been developed. Titanium oxide used inthe device is stable photoelectrochemically, and superior as anelectrode material of a metal oxide semiconductor. However, titaniumoxide has an inferior spectrum matching sunlight, and it is not expectedto have high efficiency, because it has a bandgap as large as 3.0 eV.

Therefore, an organic dye is utilized to be adsorbed onto the surface oftitanium oxide, to sensitize it. It is known that the adsorbed dye has asensitizing effect, and that titanium dioxide which has a large specificsurface area as the electrode of a photo-semiconductor, is used toimprove the efficiency of utilization of light (JP-A-1-220380 (“JP-A”means unexamined published Japanese patent application.)). Also, it isknown to use a thin film of titanium dioxide having micropores on thesurface thereof (JP-A-8-99041). However, titanium dioxide has a largeforbidden band and therefore cannot absorb light in the visible region.It is therefore necessary to coat titanium dioxide with aphotosensitizer that absorbs light in a wavelength range in 300 to 2000nm, to aim at sunlight, and an organic dye is used for this purpose.

As the organic dye, many compounds, such as xanthene-series dyes,cyanine-series dyes, basic dyes, porphyrin-series compounds, azo dyes,and Ru complexes, are known (JP-A-11-144772 and JP-T-7-500630 (“JP-T”means a publication of the translation of an international patentapplication.)). It has been considered that a solar cell, which iscoated with an Ru complex and is sensitized with a dye, has a highphotoelectric conversion efficiency, and that such the solar cell isproduced at lower costs in contrast to even a silicon solar cell.Although these points are advantageous, the performance of a celldepends on a sensitizing dye, and it is desired to develop ahigh-performance dye upon developing a high-performance cell.

An object of the present invention is to provide a dye having high lightabsorbance over a wide wavelength range. Another object of the presentinvention is to provide a photoelectric conversion element using thedye. A further object of the present invention is to provide aphotochemical cell using the element.

Other and further objects, features, and advantages of the inventionwill appear more fully from the following description, taken inconnection with the accompanying drawings.

DISCLOSURE OF THE INVENTION

The inventors of the present invention, having made earnest studies onthe above objects, developed a dye which is composed of a novelβ-diketonate metal complex and found that light in a wide wavelengthrange (less than 800 nm) can be absorbed by this dye, to complete thepresent invention.

Accordingly, according to the present invention the following inventionsare provided.

(1) A metal complex having a β-diketonate represented by the followingformula (1):

wherein M represents a metal atom of the VIII group; R¹, R² and R³ eachrepresent a group or an atom select the group consisting of an alkylgroup, an aryl gr hydroxyl group, an amino group, an alkoxy group, ahydrogen atom and a halogen atom; X⁻¹ represents an ion selected from ahalogen ion, a nitric acid ion, a sulfonic acid ion, a fluoroboric acidion, a fluorophosphoric acid ion and a perchloric acid ion; and L¹ or L²respectively represents a 2,2′-bipyridine group or a 1,10-phenanthrolinegroup, each of which may be substituted with a group or an atom selectedfrom an alkyl group, a carboxyl group, a sulfonic acid group, aphosphonic acid group, a hydroxyl group, an amino group, a hydrogen atomand a halogen atom.

(2) A metal complex having a β-diketonate represented by the followingformula (2):

wherein M represents a metal atom of the VIII group; R¹, R² and R³ eachrepresent a group or an atom selected from the group consisting of analkyl group, an aryl group, a hydroxyl group, an amino group, an alkoxygroup, a hydrogen atom and a halogen atom; and L¹ or L² respectivelyrepresents a 2,2′-bipyridine group or a 1,10-phenanthroline group, inwhich one or both of L¹ or L² may be substituted with an acidic groupselected from a carboxyl group, a sulfonic acid group, a phosphonic acidgroup and a hydroxyl group each of which is neutralized.

(3) A method for producing a metal complex having a β-diketonaterepresented by the following formula (1), comprising heating a metalcomplex of the VIII group having, as a ligand, L¹ L² which represent a2,2′-bipyridine group or a 1,10-phenanthroline group (these groups maybe substituted with a group or an atom selected from an alkyl group, acarboxyl group, a sulfonic acid group, a phosphonic acid group, ahydroxyl group, an amino group, a hydrogen atom and a halogen atom), anda β-diketone derivative, in the presence of an alkali and a solvent, andtreating the resulting product with an aqueous solution containing anacid.

(4) A method for producing a metal complex having a βdiketonaterepresented by the following formula (2), comprising adding an alkali tothe aqueous solution containing the β-diketonate described in the aboveitem (3).

(5) A photoelectric conversion element, which comprises a porous oxidesemiconductor layer laminated on a layer composed of an electricconductor, and the metal complex as stated in the above item (1) or (2)adsorbed to the porous oxide semiconductor layer.

(6) A photochemical cell, which comprises the photoelectric conversionelement as stated in the above item (5), a counter electrode, and acharge-transfer layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing the layer structure of a preferredphotochemical cell according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be further explained hereinafter.

A novel metal complex of the present invention is a metal complex havingthe following structure and two types of β-diketonate.

(1) A metal complex having a β-diketonate represented by the followingformula (1):

wherein M represents a metal atom of the VIII group, R¹, R² and R³represent groups or atoms selected from the group consisting of an alkylgroup, an aryl group, a hydroxyl group, an amino group, an alkoxy group,a hydrogen atom and a halogen atom, X⁻¹ represents an ion selected froma halogen ion, a nitric acid ion, a sulfonic acid ion, a fluoroboricacid ion, a fluorophosphoric acid ion and a perchloric acid ion and L¹or L² respectively represents a 2,2′-bipyridine group or a1,10-phenanthroline group where these groups may be substituted with agroup or an atom selected from an alkyl group, a carboxyl group, asulfonic acid group, a phosphonic acid group, a hydroxyl group, an aminogroup, a hydrogen atom and a halogen atom.

(2) A metal complex having a β-diketonate represented by the followingformula (2):

wherein M represents a metal atom of the VIII group, R¹, R² and R³represent groups or atoms selected from the group consisting of an alkylgroup, an aryl group, a hydroxyl group, an amino group, an alkoxy group,a hydrogen atom and a halogen atom, and L¹ or L² respectively representsa 2,2′-bipyridine group or a 1,10-phenanthroline group where one or bothof L¹ or L² may be substituted with an acid group selected from acarboxyl group, a sulfonic acid group, a phosphonic acid group and ahydroxyl group which are neutralized.

The above-mentioned compounds will be explained in more detail.

The metal of the above metal complex is a metal of the VIII group.Metals of the VIII group include elements of iron, cobalt, nickel,ruthenium, rhodium, palladium, osmium, iridium and platinum. As themetal of the metal complex, a metal which is properly selected fromthese VIII group metals may be used.

R¹, R² and R³ are groups or atoms selected from alkyl groups, arylgroups, hydroxyl groups, amino groups, aminoalkyl groups in which a partof amino group is substituted with an alkyl group), alkoxy groups, ahydrogen atom and halogen atoms. The alkyl group is an aliphaticsaturated hydrocarbon group which may have a straight-chain or branchedchain. Given as specific examples of the alkyl group are a methyl group,ethyl group, propyl group, i-propyl group and groups of n-butyl,i-butyl, sec-butyl and tert-butyl. The number of the carbons of thealkyl group may be optionally selected as far as it does not disturb theproduction of a metal complex. As to the number of carbons in the alkylgroup, alkyl groups whose carbon number is in a range from 1 to 10 aregenerally selected. The aryl group represents a group obtained byremoving one hydrogen atom from an aromatic hydrocarbon, specifically, aphenyl group, a group such as a tolyl group and xylyl group in which aphenyl group may be substituted with an alkyl group such as a methylgroup or ethyl group, biphenyl group, naphthyl group, anthryl group,phenanthryl group. The alkoxy group is a group in which oxygen is bondedto an alkyl group and specific examples of the alkoxy group may includea methoxy group, ethoxy group, propoxy group, butoxy group, pentyloxygroup and hexyloxy group. Specific examples of the halogen atom mayinclude chlorine, fluorine, bromine and iodine.

X⁻¹ represents a negative monovalent ion. The halogen ion isspecifically an ion of a halogen atom selected from chlorine, fluorine,bromine and iodine.

L¹ or L² respectively represent a 2,2′-bipyridine group

or a 1,10-phenanthroline group.

These groups may be substituted with a substituent R. The substituent Rmay be substituted with a group or atom selected from an alkyl group(those having 1 to 10 carbon atoms and a straight chain or branchedchain), carboxyl group, sulfonic acid group, phosphonic acid group,hydroxyl group, amino group, hydrogen atom and halogen atom. Thesubstituent R may be substituted not only with one substituent but alsowith two or more substituents.

The structural formula of the β-diketonate as the ligand is specificallyshown as follows.

In the above formulae, R has the same meaning as defined in R¹, R² or R³of the above-mentioned β-diketonate.

Specific examples of the structural formula of the metal complex havingthe β-diketonate represented by the mentioned formula (1), are shownbelow.

Specific structural formulas of the metal complex having theβ-diketonate represented by the above-mentioned formula (2), are shownbelow.

A process for producing the metal complex having a β-diketonaterepresented by the above formula (1) is explained below. A process forproducing a metal complex having a β-diketonate shown by the followingformula (1), the process comprising heating a metal complex of the VIIIgroup having, as a ligand, L¹ L² which represent a 2,2′-bipyridine groupor a 1,10-phenanthroline group (these groups may be substituted with agroup or an atom selected from an alkyl group, a carboxyl group, asulfonic acid group, a phosphonic acid group, a hydroxyl group, an aminogroup, a hydrogen atom and a halogen atom) and a β-diketone derivativein the presence of an alkali and a solvent, and then treating theresulting product with an aqueous solution containing an acid.

The raw material is a metal complex of the VIII group having, as aligand, a group containing L¹ L² which represent a 2,2′-bipyridine groupor a 1,10-phenanthroline group (these groups may be substituted with agroup or an atom selected from an alkyl group, a carboxyl group, asulfonic acid group, a phosphonic acid group, a hydroxyl group, an aminogroup, a hydrogen atom and a halogen atom), and a β-diketone or itsderivative. All these compounds are known compounds.

As the metal, ruthenium, iron, cobalt, nickel, palladium or platinum canbe used. Examples of the β-diketone may include acetylacetone.

As examples of the β-diketone derivative, the following compounds may begiven.

In the above formulae, R has the same meaning as defined in R¹, R² or R³of the above-mentioned β-diketonate.

The solvent may be any one of those which can solubilize the metalcomplex and specific examples of the solvent may include water, amixture of dimethylformamide and water and alcohol.

The alkali is used to generate the β-diketonate which is an anionic typeand, specifically, sodium carbonate, sodium hydroxide, sodium alkoxideor the like can be used as the alkali. The acid used in the abovereaction serves to neutralize the reaction system and to add an ion X tothe complex obtained. X is a group selected from a halide ion, nitricacid ion, sulfonic acid ion, fluoroboric acid ion, fluorophosphoric acidion and perchloric acid ion. The acid is acids having these Xs. Specificexamples of the acid may include hydrochloric acid, hydrofluoric acid,hydrobromic acid, nitric acid, trifluoromethanesulfonic acid,toluenesulfonic acid, tetrafluoroboric acid, hexafluorophosphoric acidand perchloric acid.

It is effective to carry out the heating in reflux condition.

The reaction scheme is shown as follows.

For example, when the object product to be obtained is a ruthenium metalcomplex, its ligand L¹ L² as is 2,2′-bipyridine-4,4′-dicarboxylic acid,R¹ and R³ are methyl groups, R² is a hydrogen atom and X⁻ is aperchloric acid ion, the ruthenium metal complex is produced as follows.

As the VIII group metal complex,cis-dichlorobis(2,2′-bipyridine-4,4′-dicarboxylic acid) ruthenium isused and as the β-diketone, acetylacetone is used.

A metal complex cis-dichlorobis(2,2′-bipyridine-4,4′-dicarboxylic acid)ruthenium is dissolved in a solvent to use. As the solvent, any one ofthose which can dissolve the above-mentioned VIII group metal complexcan be optionally used. Specifically, a mixed solvent ofdimethylformamide and water etc. can be used. As the alkali, any one ofthose which can produce the β-diketonate can be optionally utilized.Specific examples of the alkali may include sodium carbonate.

Heating is required for the reaction and therefore the raw materials areheated under reflux.

The product obtained with the above-mentioned treatments is dried, andan aqueous perchloric acid solution which is an aqueous solutioncontaining X⁻ is added to the dried product to run a reaction. Afterthat, when the reaction mixture is put in an acidic condition, aprecipitate is produced. The precipitate is separated by filtration andwashed with methanol, followed by drying, and the object product can beobtained.

The above reaction is shown as follows.

For the production of the metal complex having the β-diketonate as shownin the above-described formula (2), the metal complex containing theβ-diketonate represented by the above-described formula (1) is producedand the resulting compound is treated by a base to produce the metalcomplex. As specific examples of the base, sodium hydroxide and ammoniamay be given. Additionally, the product obtained in the stage prior tothe treatment using the aqueous solution containing X⁻ can be used.

The photoelectric conversion element of the present invention is formedwith forming an oxide semiconductor layer on a conductive substratewhich is composed of a conductive material and adsorbing theabove-mentioned metal complex having the β-diketonate of the presentinvention to the oxide semiconductor layer.

As the conductive material, a metal, carbon, conductive polymer orconductive glass can be used. These materials can be used whether theyare light-transmittable or not. Generally, as to the transmittance,conductive materials having a light-transmittance of 80% or more arepreferably used in general. Conductive materials having a plate-likeform or a sheet-like form can be used. These materials act as a support.In the case of using conductive glass, a film of a conductive metaloxide made of tin oxide or indium/tin complex oxide can be formed on thesurface of glass to use. Further, a conductive layer of a metal orcarbon may be formed on conductive substrate to use. It is preferablethat the surface resistance of the conductive substrate is generally avalue of 10 Ω/cm² or less.

In case that the oxide semiconductor layer formed on the surface of theabove-mentioned conductive material is formed, a dispersion solution inwhich a fine particle of the oxide semiconductor is dispersed in asolvent is produced, and this dispersion solution is allowed to adheredto the surface of the conductive material, followed by baking, to form athin film composed of the oxide semiconductor.

As the oxide semiconductor to be used, an oxide of a transition metalsuch as titanium, niobium, zinc, tin, zirconium, yttrium, lanthanum ortantalum is used. Perovskite type oxides such as strontium titanate andcalcium titanate can be also used. These semiconductors bring about verypreferable results.

The finer the primary particle diameter of these semiconductor oxidesis, the more preferable results are brought about.

The particle diameter is in a range from generally 1 to 5000 nm andpreferably 2 to 50 nm.

As the solvent used to disperse this fine particulate-like semiconductoroxide in the solvent, any one of solvents which can be dispersed each ofthese oxide semiconductors can be optionally used. As the solvent, asolvent selected from water, an organic solvent, and water and anorganic solvent can be used. As the organic solvent, a hydrocarbon,alcohol, ether, ketone, ester or the like can be used.

In order to better the dispersion of the semiconductor oxide, varioussurfactants and a viscosity modifier can be used. As specific examplesof the viscosity modifier, polyethylene glycol can be given.

The oxide semiconductor layer is baked in the presence of air in thecondition of a temperature of 1000° C. or less. A temperature rangebetween generally 300 and 800° C. and preferably 400 and 600° C. isadopted.

As the layer which is composed of the oxide semiconductor, a layer whichhas about 5 to 100 μm as thickness after baked is required. The oxidesemiconductor layer obtained in this manner form a fine porous layer.

The oxide semiconductor layer formed on the above-mentioned conductivesubstrate is immersed in the dye dissolved in a solvent, so that a dyecomposed of the above-mentioned metal complex having the β-diketonate inthe present invention is allowed to adsorb to the semiconductor oxidelayer. As the solvent for the dye, methanol, acetonitrile,dimethylformamide, water or the like can be used. The concentration ofthe dye in the solvent is appropriately selected from the range from10⁻⁵ to 10⁻² M to use. An optimum concentration differs depending uponthe type of dye. The immersing time is in a range from generally 0.5 to24 hours and is appropriately selected within the order of this rangeaccording to the need.

As the immersing temperature, a temperature ranging from roomtemperature to 100° C. is appropriately selected in general.

The photocell of the present invention will be explained with referenceto FIG. 1.

The photocell is composed of a counter electrode formed on the surfaceof a conductive substrate 1, and it is further constituted by a layerstructure thereon comprising a thin film layer composed of adye-carrying oxide semiconductor film 2, which is formed by absorbing adye to an oxide semiconductor, a charge-transfer layer 3, and a counterelectrode 4.

As the counter electrode, one obtained by forming a thin layer ofplatinum, rhodium, ruthenium, ruthenium oxide or carbon etc. on aconductive material or a conductive substrate is used.

As the charge transfer layer, a layer formed with an electrolyticsolution containing a redox material in an organic solvent is used. Asthe redox material, a combination of, for example, I⁻/I₃ ⁻, Br⁻/Br₃ ⁻,Fe²⁺/Fe³⁺, Sn²⁺/Sn⁴⁺, Cr²⁺/Cr³⁺, V²⁺/V³⁺ or quinone/hydroquinone isused.

As specific examples of the organic solvent, acetonitrile,propionitrile, ethylene carbonate and propylene carbonate may be given.As this charge transfer layer, a gel electrolyte obtained by solidifyingthe electrolytic solution of the liquid charge-transfer layer which iscomposed of the above-mentioned electrolytic solution, or a solidhigh-molecular electrolyte containing a redox substance in a highmolecular substance can be used.

The metal complex which is obtained according to the present inventionand has the β-diketonate as a ligand is a dye which is composed of ametal complex exhibiting high light absorbance in the visible radiationregion. Utilizing this characteristic, a photoelectric conversionelement which makes use of visible rays can be obtained. Thephotochemical cell using this photoelectric conversion element exhibitsa high photoelectric conversion efficiency.

EXAMPLES

The present invention will be described in more detail based on theexamples given below, but the present invention is not meant to belimited by these examples.

Example 1

73 mg of cis-dichlorobis(2,2′-bipyridine-4,4′-dicarboxylicacid)ruthenium was dissolved in 15 ml of a solvent consisting ofdimethylformamide and water (2:1). 203 mg of sodium carbonate wasfurther added to the mixture, which was then stirred sufficiently. 0.10ml of acetylacetone was added to the mixture and the resulting mixturewas heated under refluxing over 3 hours. The resulting mixturecontaining the reaction product was dried by evaporation. A small amountof water was added and then an aqueous solution of dilute perchloricacid was added to the dried mixture to obtain an acidic solution.

After the solution was allowed to stand, the produced precipitate wasseparated by filtration, washed with methanol and dried to obtain 49 mgof a target ruthenium complex containing a β-diketonate.

The product obtained according to the above-mentioned manner wasanalyzed in terms of elemental analysis, mass spectrometry, NMR andmeasurements of infrared and visible-ultraviolet absorption and as aresult, it was confirmed that the product had the following structuralformula. M was a ruthenium metal, L¹ and L² were both2,2′-bipyridine-4,4′-dicarboxylic acids, R¹ and R³ were methyl groups,R² was a hydrogen atom and X⁻ was a perchloric acid ion.

Example 2

The product obtained in the above Example 1 was suspended in water, towhich was then added an aqueous concentrated ammonia solution. Theresulting solution was dried to obtain a target ruthenium complexcontaining a β-diketonate.

The product obtained according to the above-mentioned manner wasanalyzed in terms of elemental analysis, mass spectrometry, NMR andmeasurements of infrared and visible-ultraviolet absorption and as aresult, it was confirmed that the product had the following structuralformula. M was a ruthenium metal, L1 and L2 were bothammonium-2,2′-bipyridine-4,4′-dicarboxylic acids, R¹ and R³ were methylgroups and R² was a hydrogen atom.

Example 3 Production of a Photoelectric Conversion Element

12 g of titanium oxide (P-25, manufactured by Nippon Aerosil Co., Ltd.,surface area: 55 m²/g, average primary particle diameter: 50 nm or less)was added to 0.4 ml of acetylacetone, 20 ml of water and 0.2 ml of adispersant (Triton X-100, manufactured by Aldrich) to prepare adispersion solution. This dispersion solution was applied to aconductive glass substrate (SnO₂, ₁₀ Ω/cm²) of 1 mm in thickness andbaked in air under the condition of 500° C. for one hour. The resultingthin film of titanium oxide was immersed at room temperature for 12hours, in a solution containing the β-diketonate ruthenium complexobtained in Example 1 in a concentration of 1 mM.

Example 4 Production of a Photochemical Cell

One counter electrode produced by vapor depositing platinum, asemiconductor thin film as produced in the above-mentioned Example 3, anacetonitrile solution layer containing iodine (0.1 M) and lithium iodide(0.5 M) as a charge layer and further another counter electrode weredisposed on a conductive glass substrate (SnO₂, 10 Ω/cm²), to produce aphotochemical cell.

The photochemical cell thus obtained was irradiated with pseudo sunlight (1,000 w/m²) using a solar simulator (manufactured by WACOM Co.,Ltd.) to obtain a photocurrent of 13.2 mA/cm², a photovoltage of 0.74 Vand a photoelectric conversion efficiency of 6.0%.

INDUSTRIAL APPLICABILITY

The metal complex containing the β-diketonate as a ligand which isobtained according to the present invention is a dye which is composedof a metal complex exhibiting high light absorbance in the visibleradiation region and is therefore a suitable material to obtain aphotoelectric conversion element utilizing visible rays by making use ofthese characteristics. A photochemical cell using this photoelectricconversion element exhibits a high photoelectric conversion efficiency.

Having described our invention as related to the present embodiments, itis our intention that the invention not be limited by any of the detailsof the description, unless otherwise specified, but rather be construedbroadly within its spirit and scope as set out in the accompanyingclaims.

What is claimed is:
 1. A metal complex having a β-diketonate representedby the following formula (1)

wherein M represents a metal atom of the VIII group; R¹, R² and R³ eachrepresent a group or an atom selected from the group consisting of analkyl group, an aryl group, a hydroxyl group, an amino group, an alkoxygroup, a hydrogen atom and a halogen atom; X⁻ represents an ion selectedfrom a halogen ion, a nitric acid ion, a sulfonic acid ion, afluoroboric acid ion, a fluorophosphoric acid ion and a perchloric acidion; and L¹ and L² represent a 2,2′-bipyridine group or a1,10-phenanthroline group, each of which is substituted with at leastone group or one atom selected from a carboxyl group, a sulfonic acidgroup, a phosphonic acid group, a hydroxyl group, an amino group, and ahalogen atom.
 2. A metal complex having a β-diketonate represented bythe following formula (2):

wherein M represents a metal atom of the VIII group; R¹, R² and R³ eachrepresent a group or an atom selected from the group consisting of analkyl group, an aryl group, a hydroxyl group, an amino group, an alkoxygroup, a hydrogen atom and a halogen atom; and L¹ and L² represent a2,2′-bipyridine group or a 1,10-phenanthroline group, in which one orboth of L¹ and L² is substituted with an acidic group selected from acarboxyl group, a sulfonic acid group, a phosphonic acid group and ahydroxyl group each of which is neutralized.
 3. A method for producing ametal complex having a β-diketonate represented by the formula (1),

comprising heating a metal complex of the VIII group having, as ligands,L¹ and L² which represent a 2,2′-bipyridine group or a1,10-phenanthroline group, each of which is substituted with at leastone group or one atom selected from a carboxyl group, a sulfonic acidgroup, a phosphonic acid group, a hydroxyl group, an amino group, and ahalogen atom, wherein M represents a metal atom of the VIII group; R¹,R² and R³ each represent a group or an atom selected from the groupconsisting of an alkyl group, an aryl group, a hydroxyl group, an aminogroup, an alkoxy group, a hydrogen atom and a halogen atom; and aβ-diketonate derivative, in the presence of an alkali and a solvent, andtreating the resulting product with an aqueous solution containing anacid such that X⁻ represents an ion selected from the group consistingof a halogen ion, a nitric acid ion, a sulfonic acid ion, a fluoroboricacid ion, a fluorophosphoric acid ion, and a perchloric acid ion.
 4. Amethod for producing a metal complex having a β-diketonate representedby the formula (2),

further comprising adding an alkali to the aqueous solution containingthe β-diketonate described in claim
 3. 5. A photoelectric conversionelement, which comprises a porous oxide semiconductor layer laminated ona layer composed of an electric conductor, and the metal complex asclaimed in claim 1 or 2 adsorbed to the porous oxide semiconductorlayer.
 6. A photochemical cell, which comprises the photoelectricconversion element as claimed in claim 5, a counter electrode, and acharge-transfer layer.
 7. The metal complex of claim 1, wherein M isselected from the group consisting of iron, cobalt, ruthenium, rhodium,palladium, osmium, iridium, and platinum.
 8. The metal complex of claim1, wherein X⁻ is an ion selected from the group consisting of a halogenion, a nitric acid ion, a sulfonic acid ion, a fluoroboric acid ion, anda fluorophosphoric acid ion.
 9. The metal complex of claim 2, wherein Mis selected from the group consisting of iron, cobalt, ruthenium,rhodium, palladium, osmium, iridium, and platinum.
 10. The method ofclaim 3, wherein the β-diketonate derivative is selected from the groupconsisting of

wherein R is an alkyl group or a hydrogen atom.
 11. The method of claim3, wherein the acid is selected from the group consisting ofhydrochloric acid, hydrofluoric acid, hydrobromic acid, nitric acid,trifluoromethanesulfonic acid, toluenesulfonic acid, tetrafluoroboricacid, hexafluorophosphoric acid, and perchloric acid.
 12. The method ofclaim 3, wherein the acid is hydrochloric acid, hydrofluoric acid,hydrobromic acid, nitric acid, trifluoromethanesulfonic acid,toluenesulfonic acid, tetrafluoroboric acid, or hexafluorophosphoricacid.